diff --git a/configure.ac b/configure.ac
index 2d342faf2db..714b186cccc 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2,7 +2,7 @@
 ## Ed Hartnett 8/16/17
 
 # Initialize autoconf and automake.
-AC_INIT(pio, 2.4.2)
+AC_INIT(pio, 2.4.2-development)
 AC_CONFIG_SRCDIR(src/clib/pio_darray.c)
 AM_INIT_AUTOMAKE([foreign serial-tests])